Overweight in children 6 to 23 mos. has almost doubled in the last 30 years. Overweight developed early in childhood has been shown to track into adulthood, increasing the risk for weight related disease (CVD, diabetes). New first time mothers create the eating and physical activity (PA) environment for themselves and their baby, thereby increasing the risk for or protecting against the development of overweight. In order to better understand factors contributing to the development of overweight in very young children, we propose a prospective observational cohort study of 120 healthy new mother and baby pairs (50 percent Black, 50 percent pre-pregnancy BMIe25, full range SES) who will be recruited from the 3rd trimester of pregnancy up to the baby's 2nd mo. well child visit from the Central Savannah Region and followed until the baby's 1st birthday. Assessments will be coordinated with well child visits, taking place at doctors'offices, mothers'homes and by phone. We will characterize new mothers'eating, PA and infant feeding practices, and establish associations between protective lifestyle behaviors, maternal and contextual factors and healthy weight status for mothers (BMI<25) and babies (<95 percent weight for age/gender) and risk factors for the babies and mothers who are likely to become (or remain) overweight at 6 and 12 mos. Specifically we will identify factors which are associated with or prevent mothers and babies from eating 5-9 servings of fruits and vegetables a day, and mothers achieving CDC/ACSM guidelines for healthy PA during the first year of their babies'lives. We will use questionnaires, diet and PA recalls and accelerometry to measure mothers'self-efficacy and social support for healthy lifestyle behavior, beliefs and intentions regarding the creation of a healthy food and PA environment for their child, parenting stress, knowledge about and actual eating and PA, and energy expenditure. As an exploratory aim we will investigate gene (G-protein ss3 subunit C825 T and serotonin transporter 5-HTTLPR polymorphisms obtained via buccal swabs) by environment associations between postpartum weight, eating and PA patterns and parenting stress. We will also explore the relationship between presence or absence of the G-protein ss3 subunit C825 T and weight gain in the babies. Data will be analyzed using logistic regression to identify candidate risk and protective factors for dichotomized outcomes, after adjusting for significant maternal and baby characteristics. Path analysis will be used to examine the validity of hypothesized causal pathways involving continuous measures. Two-group comparison methods and analysis of covariance will be used to investigate gene by environment associations. Results will be used to develop a family based Primary Prevention intervention to prevent Overweight Development in very young children. (P-POD) PUBLIC HEALTH RELEVANCE: Obesity is a major public health concern in the US, with health care costs increasing in proportion to weight related disease (CVD, diabetes). Interventions to facilitate weight loss have, on balance, been unsuccessful. Prevention of early weight gain can lead to prevention of childhood and adult obesity, and weight related disease. As mothers are often the primary mode of transmission of eating and activity patterns to very young children, identification of family based mechanisms contributing to or preventing overweight development could lead to successful interventions which could help to ameliorate this public health problem.